The invention relates to an apparatus for shaping sheet material, more particularly for manufacturing of propellers for ships, said apparatus comprising a top part and a bottom part, each built up by abutting members.
Considering that ships' propellers have to be resistant to the chemical influence exerted by the sea water, bronze casting is usually applied when manufacturing such propellers. These ships' propellers are designed as a helicoid. However, due to the immense forces in question, and because of strength, the cross section of the propeller increases toward the root, and this results in a smaller pitch of the helicoid at the front surface of the propeller than at the back surface of same. Among other things, this condition is a contributory cause of reducing the efficiency of the propeller.
In order to overcome this disadvantage, it has been proposed to manufacture propellers of sheet material, for instance rustless steel plate, thereafter welding said propellers to a boss. However, the hitherto known methods of shaping such plate material have not yet been economically sound, and therefore such ships' propellers have not been greatly introduced.
Therefore, the purpose of the present invention is to provide an apparatus whereby the manufacturing of ships' propellers can be carried out at a more favorable price by reducing the costs of the apparatus to a minimum.